Merge pull request #1 from dwursteisen/fix_rotation

[ROTATION] Fix rotation sign
minigdx · Jul 7, 2020 · a7e1874 · a7e1874
2 parents 05ad83d + c2c56fa
commit a7e1874
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Showing 3 changed files with 26 additions and 14 deletions.
diff --git a/src/commonMain/kotlin/com/curiouscreature/kotlin/math/Matrix.kt b/src/commonMain/kotlin/com/curiouscreature/kotlin/math/Matrix.kt
@@ -16,8 +16,6 @@
 
 package com.curiouscreature.kotlin.math
 
-import kotlin.math.asin
-import kotlin.math.atan2
 import kotlin.math.cos
 import kotlin.math.sin
 import kotlin.math.tan
@@ -320,16 +318,8 @@ data class Mat4(
         get() = w.xyz
     val rotation: Float3
         get() {
-            val x = normalize(right)
-            val y = normalize(up)
-            val z = normalize(forward)
-
-            return when {
-                z.y <= -1.0f -> Float3(degrees(-HALF_PI), 0.0f, degrees(atan2(x.z, y.z)))
-                z.y >= 1.0f -> Float3(degrees(HALF_PI), 0.0f, degrees(atan2(-x.z, -y.z)))
-                else -> Float3(
-                    degrees(-asin(z.y)), degrees(-atan2(z.x, z.z)), degrees(atan2(x.y, y.y)))
-            }
+            val toEulerAngles = Quaternion.from(this).toEulerAngles()
+            return Float3(degrees(toEulerAngles.x), degrees(toEulerAngles.y), degrees(toEulerAngles.z))
         }
 
     inline val upperLeft: Mat3

diff --git a/src/commonMain/kotlin/com/curiouscreature/kotlin/math/Quaternion.kt b/src/commonMain/kotlin/com/curiouscreature/kotlin/math/Quaternion.kt
@@ -14,16 +14,20 @@ data class Quaternion(val x: Float, val y: Float, val z: Float, val w: Float) {
         return floatArrayOf(x, y, z, w)
     }
 
-    // https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles#Source_Code_2
+    /**
+     * Transform a quaternion in Euler angles.
+     * Angles are in degrees.
+     */
     fun toEulerAngles(): Float3 {
+        // https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles#Source_Code_2
         // roll (x-axis rotation)
         val sinrCosp = 2f * (w * x + y * z)
         val cosrCosp = 1f - 2f * (x * x + y * y)
         val roll = atan2(sinrCosp, cosrCosp)
 
         // pitch (y-axis rotation)
         val sinp = 2f * (w * y - z * x)
-        val pitch = if (abs(sinp) >= 1)
+        val pitch = if (abs(sinp) >= 1f)
             PI / 2f * sign(sinp) // use 90 degrees if out of range
         else
             asin(sinp)

diff --git a/src/commonTest/kotlin/com/curiouscreature/kotlin/math/MatrixTest.kt b/src/commonTest/kotlin/com/curiouscreature/kotlin/math/MatrixTest.kt
@@ -243,6 +243,24 @@ class MatrixTest {
         )
     }
 
+    @Test
+    fun Mat4_rotation_by_axis_x() {
+        val x = rotation(Float3(1f, 0f, 0f), 90f).rotation.x
+        assertEquals(-90f, x, delta = 0.1f)
+    }
+
+    @Test
+    fun Mat4_rotation_by_axis_y() {
+        val y = rotation(Float3(0f, 1f, 0f), 90f).rotation.y
+        assertEquals(-90f, y, delta = 0.1f)
+    }
+
+    @Test
+    fun Mat4_rotation_by_axis_z() {
+        val z = rotation(Float3(0f, 0f, 1f), 90f).rotation.z
+        assertEquals(-90f, z, delta = 0.1f)
+    }
+
     @Test
     fun normal() {
         assertArrayEquals(